Dissertation vs Thesis: What Is the Difference in the US, UK and Elsewhere?

In the US, a dissertation is usually the long research project you complete for a doctorate, while a thesis is usually the shorter project that finishes a master’s degree. In the UK the words swap: a thesis is the written work for a research degree such as a PhD, and a dissertation is usually the final project of a bachelor’s or taught master’s degree.

That split follows the definitions used by the University of Mississippi Graduate School and the University of Strathclyde library, while Australian universities such as Melbourne mostly say thesis, even for the PhD. Each school writes its own rules, though, so your program handbook decides which word, word limit and exam apply to you.

TL;DR

• US: dissertation for the doctorate, thesis for the master’s. UK: the reverse, with thesis reserved for research degrees.

• Ireland, Australia and the University of Toronto also say thesis for the PhD. The University of the Philippines Diliman follows the US pattern.

• A thesis is a full research document. A thesis statement is one or two sentences that state an argument.

• Word limits and final exams differ by university and even by department, so your handbook has the last word.

Dissertation vs thesis: key differences

The name changes by country, but the work at each level stays much the same, so this table compares them by level. The source behind every cell is linked in the sections below.

Which word does each country use?

United States

US graduate schools tie the word to the degree. The University of Mississippi Graduate School says thesis “has come to be used” for the master’s document, while dissertation “has been applied to the doctorate.” Cornell’s Graduate School pairs them the same way when it requires the “completion and defense of the master’s thesis or doctoral dissertation.”

Not every US master’s needs a thesis. At UC Santa Barbara, Plan I requires one, while Plan II replaces it with a comprehensive exam or a project.

A US doctorate ends with an oral defense. At the University of Michigan, Rackham Graduate School requires a dissertation committee of at least four members and announces each defense publicly, so others can follow it on Zoom.

United Kingdom

In the UK, thesis signals a research degree. The University of Strathclyde library defines a dissertation as independent research at undergraduate or taught postgraduate level, and a thesis as work for a research degree such as a PhD, MLitt or MRes. The University of Essex library draws the same line, and both note that the words are often used interchangeably.

A UK PhD ends with a viva, short for viva voce. The Quality Assurance Agency (QAA) describes it as an oral examination at which you defend the thesis, with at least one examiner from outside your university. Many universities let your supervisor observe, but supervisors play no active role in the decision. At Cambridge’s Department of Engineering, the viva is usually you and two examiners, one internal and one external.

Australia

Australian universities mostly say thesis, including for honours. The University of Melbourne examines both PhD and research master’s work as theses, and the Australian National University’s honours course in arts and social sciences is simply called Thesis.

Exam formats can change, too. Melbourne examines research master’s theses on the written work alone, but PhD candidates who started on or after 1 January 2025 must sit a viva unless a waiver is approved. Its viva process gives the two examiners one to two hours with the candidate.

Ireland, Canada and the Philippines

Ireland follows the UK. Trinity College Dublin uses thesis for the PhD and research master’s, and dissertation for work on taught programs. Its viva guide calls the viva “an oral defence” of the thesis, usually with an internal and an external examiner, and says the viva itself is private.

In Canada, check your own school’s wording. At the University of Toronto’s Institute of Medical Science, the PhD document is a thesis, but the final oral examination looks more like a US defense: four to six voting members, an external appraiser from another university, and usually 2.5 to 3 hours.

The Philippines follows the US pattern. The University of the Philippines Diliman’s College of Social Sciences and Philosophy sets separate rules for the master’s thesis and the doctoral dissertation, each with its own oral defense.

What is a dissertation?

A dissertation is a long, independent research project written up as a single document and submitted for a degree. In the US it is usually the doctoral version, which the University of Mississippi says must “make an original contribution.” In the UK it is more often the project that closes a bachelor’s or taught master’s, such as Durham University’s 10,000-word BA Geography dissertation.

Most empirical dissertations share the same core parts. Front matter comes first: a title page, an abstract and a table of contents. The chapters then move from the problem and research questions to a review of earlier studies, the methods, the results, a discussion of what the results mean and a conclusion. References and appendices close the document. Humanities projects often organize the middle chapters around themes or case studies instead.

The AnswerThis dissertation outline template lists these parts with a suggested word count for each chapter, and you can copy it into Word or Google Docs. Its total of 80,000 to 100,000 words fits a doctoral dissertation, so scale every chapter down if your limit is closer to 10,000.

What is a thesis, and how is it different from a thesis statement?

A thesis is also a long research document submitted for a degree, but its level depends on where you study. In the US it is usually the master’s version, which the University of Mississippi calls “a less comprehensive doctoral dissertation.” In the UK, Ireland and Australia it is the document for a PhD or research master’s.

A thesis statement is a different thing. It is one or two sentences, usually near the start of an essay or paper, that state the point you will argue. A thesis or dissertation usually contains one in its introduction, but the statement is never the whole project. Our thesis outline guide covers both: how to plan the chapters of a PhD thesis and how to write the statement those chapters defend.

How long is each, and how long does each take?

There is no universal word count. Limits change by country, by university and often by department, and some US schools set none. Cornell’s Graduate School, for example, leaves content and length to your special committee and adviser.

Word limits: real examples

• Durham University sets 10,000 words for its BA Geography dissertation.

• The London School of Economics sets 10,000 words for the MSc in Social Research Methods dissertation.

• The University of Melbourne expects about 40,000 words for an MPhil thesis (50,000 maximum) and about 80,000 for a PhD thesis (100,000 maximum), counting references.

• Trinity College Dublin caps an MLitt or MSc by research thesis at 60,000 words and says a PhD thesis should normally stay under 100,000, excluding footnotes and bibliography in both cases.

• The University of Cambridge sets PhD limits by degree committee: 60,000 words in Biology, 65,000 in Engineering and 80,000 in History, where theses “will normally be near that length.” Earth Sciences counts 275 numbered pages instead.

The same number can mean very different things. Trinity treats 100,000 words as the normal PhD ceiling, while Cambridge’s Engineering department refuses any request for more than 72,000.

Time to finish

In the US, the National Science Foundation’s Survey of Earned Doctorates puts the 2024 median at 5.7 years from starting a doctoral program to earning the degree, with engineering at 5.3 years and humanities and arts at 6.8. That clock starts at enrollment, so it covers coursework as well as the dissertation.

UK and Australian PhDs are planned around a shorter span. Cambridge lists its PhD in Spanish as 3 to 4 years full-time or 4 to 7 part-time, UKRI says its full-time studentships usually last three to four years, and Melbourne tells PhD examiners to expect a project achievable in 3 years.

Shorter projects move faster. At LSE’s Department of International History, the 10,000-word master’s dissertation is due in September, and Melbourne scopes MPhil research at 18 months to 2 years.

Can a template help you plan one?

Yes, as a starting point. If your program wants a proposal approved before you begin, our research proposal template explains what each section should cover, from the abstract and literature review to the methodology and references, and lists common reasons proposals get rejected. For the full document, use the outline above and set each chapter’s length from your handbook’s limit.

FAQs

Is a PhD a thesis or a dissertation?

Both, depending on where you study. US schools such as Cornell and Michigan call it a dissertation, while Cambridge, Trinity College Dublin and Melbourne call it a thesis.

Is a master’s thesis the same as a dissertation?

Not in the US, where the master’s thesis is the smaller project. In the UK, a taught master’s usually ends with a dissertation, so a British master’s dissertation and an American master’s thesis are close cousins.

Can I use the two words interchangeably?

In conversation, yes, and the Strathclyde and Essex libraries both note that the terms are often swapped. On forms, title pages and your CV, use the exact word your university uses.

Do all master’s programs require a thesis?

No. Some US programs offer a non-thesis route, such as UC Santa Barbara’s Plan II, which swaps the thesis for a comprehensive exam or a project.

Is a dissertation always longer than a thesis?

No. In the US it usually is, because it is the doctoral project. In the UK the reverse holds: Durham’s BA Geography dissertation is 10,000 words, while most Cambridge PhD limits fall between 60,000 and 80,000.

Once you know which document you are writing and what your limit is, open the dissertation outline template and resize each chapter to fit.